Engineering topics

Majumdar, A. K.

Publications and source records attributed to Majumdar, A. K..

23 records · Page 2

NASA NTRS2000

An Unsteady Long Bearing Squeeze Film Damper Model: Statically Eccentric Operation - Part 2

This paper, the second of a two-part series, presents results of an unsteady rotordynamic analysis of a long-bearing squeeze film damper executing orbits about an off center position using a fluid circuit approach. A series of nodes and branches represent the geometry of the flow circuit. The mass and momentum conservation equations are solved to predict the pressure distribution in the squeeze film. The motion of the bearing is simulated by the variation of geometry within the flow path. This effort represents the first modeling approach which allows for an arbitrary orbit size about an arbitrary position.

Schallhorn, P. A.↗

NASA NTRS1981

Stratospheric trace constituent profile retrievals using laser heterodyne radiometer IR limb sensing spectra

A retrieval technique for high resolution IR solar occultation limb sensing data is described for profiling stratospheric trace constituents. Remote measurement of ClO during sunset in the 24-45-km region with a 2-km height resolution is chosen as an example. Two types of instruments are considered: a laser heterodyne radiometer with line resolving spectral resolution and an interferometer spectrometer with a fixed slit width of 0.02/cm. It is pointed out that a multichannel approach is necessary with the heterodyne instrument for improved retrieval accuracy. The error analysis indicates the relative sizes of instrument noise and other sources of error in the retrieval of altitude profiles with high (2-km) vertical resolution.

Majumdar, A. K.↗

NASA NTRS1979

Infrared transmission at the 3.39 micron helium-neon laser wavelength in liquid-core quartz fibers

Infrared transmission at the 3.39 micron helium-neon laser wavelength has been measured in a tetrachloroethylene-filled fused-quartz fiber. The loss measurements were taken for three different settings of laser light intensity using a series of neutral density filters. The average value of transmission loss at this wavelength was found to be 56 dB/km.

Majumdar, A. K.↗

NASA NTRS1979

Higher-order skewness and excess coefficients of some probability distributions applicable to optical propagation phenomena

Expressions are derived for higher-order skewness and excess coefficients using central moments and cumulants up to 8th order. These coefficients are then calculated for three probability distributions: (1) Log-normal, (2) Rice-Nakagami, and (3) Gamma distributions. Curves are given to shown the variation of skewness with excess coefficients for these distributions. These curves are independent of the particular distribution parameters. This method is useful for studying fluctuating phenomena, which obey non-Gaussian statistics.

Majumdar, A. K.↗

NASA NTRS1978

Atmospheric turbulence chamber for optical transmission experiment Characterization by thermal method

Consideration is given to an atmospheric turbulence chamber designed for optical wave propagation experiments. The chamber consists of ten small electric heater/blowers with an aluminum foil screen and three screens of 2-mm aluminum wire meshes. Calculations are made of the temperature structure constant squared on the basis of temperature structure function measurements derived from a differential microthermocouple system. Values are presented for the refractive-index structure constant squared. The average wind velocity and temperature are found to be, respectively, 0.41 m/sec and 53 C. The inner and outer scales of turbulence are 5.0 mm and 6.5 cm. It is shown that the measured temperature structure function and the power spectrum of temperature fluctuations satisfy, respectively, the 2/3 and -5/3 power similarity laws in the inertial subrange. Possible chamber improvements are discussed.

Gamo, H.↗